The invention relates to a fluidtight zip fastener, having a pair of fluid-tight zip fastener carrying tapes in each case comprising a base tape with a soft covering layer of elastomer, thermoplastic or the like covering at least one surface thereof and to which is in each case sewn a continuous coupling member row in a position offset in spaced manner transversely to the carrying tape longitudinal edges in such a way that the facing borders of the soft covering layers are in contact with one another along a longitudinal plane intersecting the zip fastener at a central axis thereof and at right angles to the principal plane of the zip fastener, but projecting over said longitudinal plane to such an extent that when the coupling member rows are disengaged and the coupling member rows are engaged they are bent away from that side which carries the coupling member rows and extend roughly at right angles to the principal plane of the zip fastener, the soft covering layers of the facing borders of the two zip fastener carrying tapes projecting over the base tape engage with one another in fluidtight manner under pressure action and in which the zip fastener slider transmitting the zip fastener carrying tapes into the open and closed position in the case of longitudinal displacement, apart from a lower plate, an upper plate and a slider wedge interconnecting said two plates, has a guide border shaped in the central area of the slider wedge and extending roughly parallel between the upper plate and the lower plates and which on either side of the slider wedge separates the two first chambers receiving the coupling member rows from the two second chambers receiving the facing borders of the zip fasteners carrying tapes.
Such a zip fastener forms the subject matter of the applicant""s earlier-dated application 199 24 539.8-26, in which the disadvantages of conventional zip fasteners are eliminated and despite a simpler construction there is a perfect sealing action both against liquids and gases, even under pressure action, also over a longer time period. However, in the case of said earlier zip fastener it is not ensured in a completely satisfactory manner that the zip fastener slider, when transferred into the closed zip fastener state, also keeps the final coupling members of the coupling member row in a position ensuring a hermetic fluid seal. As on either side of a slider wedge, the slider keeps spaced apart the coupling members located there, special sealing measures must be taken in order to ensure an absolutely reliable seal in this end region.
On the basis of this, the problem of the invention is to so further develop a fluidtight zip fastener of the aforementioned type in such a way that in a relatively simple manner a full fluidtightness is ensured, also in the area of the zip fastener slider.
According to the invention this problem is substantially solved in that for increasing the sealing action of the zip fastener in the slider and end position, the interconnected two ends of the zip fastener carrying tapes are provided with a dimensionally more confined and consequently an overpressing-ensuring elastomer guiding the slider over its guide border shaped onto the slider wedge. Not only along the coupling member rows in the closed state, but also in the end region of the zip fastener the sought hermetic fluid seal is ensured between the upper plate and the lower plate as a result of the elastomer overpressing obtained.
In this connection is has proved very advantageous that on the side of the two interconnected ends of the zip fastener carrying tapes remote from the coupling member rows is injection method or vulcanized an oversize-possessing, approximately U-shaped, elastically flexible cam engaging on the underside of the slider upper plate. Although during the transfer of the slider into its end position such a cam offers a certain resistance due to the need of elastomer deformation, but as a result of an appropriate dimensioning of the flexible cam said resistance can be limited and consequently the actuating possibility of the slider can be controlled without disadvantageously limiting the quality of the seal.
It is particularly advantageous if in the U-shaped cam is formed at least one groove bounded by two adjacent protuberances, because this reduces the resistance action without impairing the sealing action.
According to another favourable development the groove extends over the two U-legs of the U-shaped cam and the crossbar connecting the latter and runs out in each case at the crossbar-remote leg end. In practice said leg end is the rear area of the slider in the closure/end position, i.e. the area up to which the coupling member rows are in the closed position and with their covering layers in a mutual sealing relationship.
Facing the front area of the slider in the closure position, i.e. in the area of the interconnected two ends of the zip fastener carrying tapes, is appropriately provided a transverse tie bar system absorbing transverse forces and protecting the zip fastener against damage on forcing apart or spreading. Appropriately the transverse tie bar system comprises at least one tension-proof, flexible thread, which is incorporated into the elastomer, thermoplastic, etc. below the cam crossbar linking the U-legs of the U-shaped cam. Advantageously an aramide thread is used as the tension-proof, flexible thread.
It is proved particularly advantageous with a view to a high loadability and correspondingly long zip fastener life for the transverse tie bar system to be provided alongside the coupling member rows in the end area of the zip fastener carrying tapes with in each case strong, flat reinforcing inserts and for the tension-proof, flexible threads to in each case run out over the reinforcing inserts or for them to be woven therein. Use is advantageously made of reinforcing inserts formed by a polyester woven fabric.